I set it as one of the skins in my system folder and now I cannot use any other skin. If I try to boot a new skin from the settings menu it sends me to the desktop where I see the backgrounds for the new skin but it freezes and no icons will show up.

If I put the card in the PC to change the skins out, then reboot the DS with the new skin folders it freezes on a white screen before the desktop even loads.

I have to return the "Vista" skin to the original folder then, and only then, will it boot again.

It said to put the skin in Skin1 on the M3real, isn't that where the default skin lives/ uses? that could be the problem - if you are game enough to try again, put it in a folder called Skin3 and try that out.